Can zinc contribute to stronger bones?
Zinc likely plays a genuine role in bone health, but whether supplementation offers any benefit in people without a deficiency has not yet been demonstrated. If you eat plant-based or already have bone problems, your zinc status is worth discussing with your doctor.
Higher zinc levels in the blood are associated with higher bone density. Two large studies based on American population data show this relationship in adults. Above a certain threshold in the blood the association is clearest: people with the highest zinc values had significantly more bone mass than those with the lowest. These are associations, not proven cause and effect.
A zinc intake of less than 3 mg per day is linked in observational research to a higher risk of bone loss, osteoporosis and bone fractures. More than one in five people appears to structurally take in too little zinc. Biologically, there is a plausible mechanism: zinc presumably inhibits bone-breaking cells and supports the formation of new bone tissue, although the results for this are not entirely consistent.
Zinc supplementation of 40 to 50 mg per day appears to be able to maintain bone density and speed up bone healing after fractures, especially in people who already have a low zinc intake. This comes from only five supplementation studies within a single narrative review, so real certainty does not yet exist. More convincing is a small hospital study in women who were already receiving osteoporosis treatment: in women with an already low zinc level, that treatment barely helped, but when they also received zinc medication, their bone density still rose to a normal level. In the group without zinc supplementation, almost 30% had bone fractures; in the group that did receive zinc, no fractures occurred. This involves 145 women in one retrospective study, so this result requires confirmation.
A point of attention for people who eat plant-based: vegans and vegetarians have on average a lower zinc intake and lower zinc levels in the blood than meat eaters. This is partly because plant-based zinc is more difficult to absorb. Vegans also have on average the lowest bone density of all dietary groups, although multiple deficiencies play a role simultaneously there, such as less calcium, vitamin B12 and iodine as well.
Based on two large cross-sectional studies (NHANES), one narrative review of 16 studies, one systematic review of 141 studies, one retrospective hospital study (n=145) and one mechanistic systematic review. No large randomised supplementation trials are available.